PBX selective caller identification authentication

ABSTRACT

The present invention uses capabilities of the advanced intelligent network (AIN) to control an authentication process of caller ID information data generated at a calling PBX system. The central office switching facility associated with the calling PBX system identifies calls therefrom that contain caller ID numbers that are not the PBX assigned telephone number. For such calls, the switching facility invokes triggers through the AIN common channel signaling network to access data base information in an Integrated Service Control Point (ISCP) and/or system LIDB for authenticating and controllably transmitting caller ID information. Unauthenticated information may be blocked or transmitted with notice that the information has not been authenticated.

RELATED APPLICATION

This application is related to application Ser. No. 08/725,349, filedOct. 1, 1996 and entitled CALLER SELECTIVE IDENTIFICATION FOR TELEPHONECALLS, and assigned to the assignee of the present application.

TECHNICAL FIELD

The present invention relates to telephone systems that convey selectivecaller line identification information to called parties and, moreparticularly, to the control of caller PBX system identification.

BACKGROUND ART

Caller ID is a telephone on-hook capability that provides a called partywith information about the caller before the incoming call is answered.Conventionally, such information includes the date and time of the calland the caller's telephone number. A data message, preceded by a channelseizure signal, is sent in conjunction with the ringing signal from thecentral office to the called party during the silent interval after thefirst 20-Hz, 2-second ringing phase.

Caller ID service is designed for use with the voice portion of existingloop connections. The digitally formatted message is transmitted througha stream of data bits of standardized digital format. The message issent once, without retransmission capability. The channel seizuresignal, sent at the beginning of each message to alert the called partyequipment of the coming information through physical connection of anappropriate interface, is typically composed of thirty continuous bytesof octal 125 (i.e., 01010101), or 250 milliseconds of a 600-Hz squarewave. Transmission of data follows thereafter and is completed prior tothe next 20-Hz ringing signal. For a detailed description of the methodand apparatus for sending the data message, reference is made to U.S.Pat. No. 4,551,581 issued to Doughty on Nov. 5, 1985.

The receiving display apparatus at a caller ID subscriber location maybe as disclosed in U.S. Pat. No. 4,582,956, issued Apr. 15, 1986. Theapparatus, which may be a part of a telephone instrument or astand-alone device, includes a line interface unit, a converter, acontrol circuit and a display unit. A frequency shift keyed (FSK) signalrepresenting the special service information is filtered from theringing signals by the line interface unit. The converter detects theFSK signal and demodulates the special service information from the FSKsignal. Following detection of the FSK signal, the control circuitreceives and stores the special service information. The storedinformation is periodically sent to the display unit to begin exhibitingthereof during the silent interval before the next ringing signal.

The caller ID service in the public switched telephone network (PSTN)offers several advantages to the called party subscriber. Identificationof the calling party, as provided by the caller ID service, allows thecalled party to screen an incoming call personally before its completionand thereby to decide whether or not it is desirable to answer the call.Nuisance calls, such as advertising and solicitation calls, can beavoided if the identity of a caller can determined before a call isanswered. Knowledge of caller identity also serves as a resource fordealing with and curtailing harassment calls.

Reference is made to U.S. Pat. No. 5,497,414, issued to Bartholomew onMar. 5, 1996, for a discussion of the advantages to the called partysubscriber as well as the countervailing disadvantageous effects on thecaller's privacy. If the caller number identity is made known to acalled party caller ID subscriber each time a call is made, the privacyafforded to a caller having an unlisted number is significantlycompromised. Similarly, any caller may find it desirable to place a callwithout revealing origination identity to the called party. In suchcase, the caller must take the risk that the called party line does notsubscribe to the caller ID service.

As a recourse, the caller in some existing systems is given the optionto block transmission of caller line origination identity to the calledparty. If the called party is a caller ID service subscriber, thedisplay unit will either indicate a caller privacy condition or remainblank. Reference is made to U.S. Pat. No. 5,161,181, issued to Zwick onNov. 3, 1992, for discussion of this concept. With caller ID blocked, acall is directed to the called party for completion in the standardmanner and the functionality of caller ID is lost, along with itsadvantages to the called party subscriber. The caller can thus retainanonymity with an increased likelihood that the called party will electnot to answer the call.

Accommodating the requirements of called party subscribers to screen theorigination of incoming calls before answering, while permitting callingsubscribers to individually control what origination information will betransmitted for placed calls, is an ongoing concern of serviceproviders. Enhancements to the basic caller ID service have furthercomplicated these considerations.

With one such enhancement the network provides the caller's name as wellas the caller's number for display at the caller ID box of the calledparty. The phrase "enhanced service" as used herein refers to thecapability of supplying both text and telephone caller numberidentification information. A caller who blocks caller ID to avoid areturn call from the called party may find benefit in transmitting thename information alone for identification purposes. Conventionally, theability to transmit name information without originating telephonenumber information is not available. Moreover, the provision ofadditional caller ID information increases the risk that misleadinginformation will be transmitted. For example, a call may be placed froma subscriber location at which several people reside. If the caller isnot the listed subscriber, the called party may not recognize theidentified caller name and choose not to answer the call. Identificationof the name of the actual caller instead of the name of the subscriberis a function that prior art telephone systems lack. Such a functionwould be a benefit both to the called party, who may know the calledparty and thus answer the call, and the calling party who is more likelyto have the call completed.

Complications also arise with callers that subscribe to distinctiveringing type services that provide a plurality of telephone numbers forthe same subscriber line. The distinctive ringing service subscriber mayreserve one number for important calls, which would be answered undermost circumstances, while using another number for less important callsthat the subscriber may choose to ignore. Alternatively, each number maybe associated with a different resident, the intended called party beingindicated by the distinctive ring. In other circumstances a subscribermay require two telephone numbers for a single line to distinguishbetween business calls and personal calls. The business name would belisted for the business number, while the subscriber's name would belisted for the personal use number.

Conventionally, one of the listings for the multiple number line isrecognized as a primary listing, the remainder as secondary listing(s).A called party subscriber to the basic caller ID service would receivefrom a multiple line calling subscriber a display of the caller'sprimary telephone number. A called party subscriber to the enhancedcaller ID service would additionally have displayed the primary nameassociated with the primary number. The calling party may not wish totransmit the primary number and its associated listed name for aparticular call. Depending upon the purpose of the call, a secondarynumber listing may be appropriate. A similar situation exists with abusiness subscriber who has a plurality of stations, each with a directdial number. A caller from one of the stations may wish to select amongseveral numbers to be displayed to the called party.

The above-identified application, Ser. No. 08/725,349, describes asystem and method for distinguishing between numbers, as well as names,in the transmission of caller identification information for anindividual call. The advanced intelligent network (AIN) is used to allowa calling party to specify what caller ID information to send to thecalled party for display. The telephone system Line Identification DataBase (LIDB) contains listings for subscribers that may each include aplurality of assigned telephone numbers and names. On an individual callbasis, a calling subscriber can control what information is to beextracted from LIDB for identification to the called party. Variousidentification options may be pre-established, the caller invoking aselected option by dialing a corresponding access code with the dialedtelephone number.

The system described above affords great flexibility to calling partieswhile safeguarding the interests of called parties to receive accurateinformation. These advantages are attributable to a large extent to thefact that the calling party identifying information, while conforming toa caller's preselected desired design, is generated by the network. Asthe information is prestored in a data base, called parties can besafeguarded against receipt of inappropriate information. The accuracyof the caller's identifying information can be verified upon storage bythe system prior to transmission in telephone calls. Such verificationneed be done only when new identifying information is entered into thedata base, as only the verified information can be transmittedthereafter. A called party thus has a reasonable expectancy that thereceived calling party information is reliable.

This safeguard of the above described system, however, is not availablefor calls placed from a PBX system, which can generate calling partyinformation data at the discretion of the private administrator, or anacting individual, on a call by call basis to be transmitted via a PBXtrunk to its associated PSTN switching facility. A calling party fromthe PBX system can simply dial out the called party number without needfor an access code as the desired calling party information can beprogrammed at the PBX. With such on premises control, there is no needfor the PBX customer to subscriber to the LIDB access selective callerID service. The calling party can thus output erroneous text informationas well as indicate an inaccurate and unverified calling party number.The receiver of such call, upon returning the call, may unintentionallyreach a third party instead of the actual calling party, to theannoyance of both the returning caller and the third party. Thisnuisance can also exist for called parties who do not subscribe tocaller ID services but invoke a "return call" service.

The need therefore exists in the prior art for system authentication ofcalling party identification information generated from PBX systems.Such a provision would prevent fraudulent use of third party informationas well as avoid common mistakes in entry of data in PBX systems. CallerID information authentication is of even greater complexity forinterLATA calls in which several transmission carriers, includinginterexchange carriers, are involved. U.S. Pat. No. 5,530,741, issued toRubin on Jun. 25, 1996, discloses a system wherein the interexchangecarrier controls provision of calling party number. Authentication bythe called party's local exchange carrier is thus dependent uponinformation under the control of other carrier(s).

DISCLOSURE OF THE INVENTION

The present invention overcomes the above noted prior art drawbacks ofPBX calling party identification service in part by providing, on a percall basis, a system correlation of received caller identificationinformation with pre-established parameters.

An advantage of the invention is that such correlation enablesauthentication of the received information so that authenticatedinformation will be transmitted to the called party with the routed calland unauthenticated information can be blocked as the call is routed.

An additional advantage of the present invention is that, instead ofblocking transmission, unauthenticated information can be transmittedwith an indication that such information has not been authenticated.With such feature, the called party may be able to detect a mistake inthe information such as, for example, a transposition of numbers. Thecalled party may be able to discern the correct calling party number byrecognizing the accurate number, having been informed of thenonauthentication, or by associating transmitted textual informationwith the accurate number.

The present invention uses capabilities of the advanced intelligentnetwork (AIN) to control the authentication process. The central officeswitching facility associated with the calling PBX system identifiescalls therefrom that contain caller ID numbers that are not the PBXassigned telephone number. For such calls, the switching facilityinvokes triggers through the AIN common channel signaling network toaccess data base information in an Integrated Service Control Point(ISCP) and/or system LIDB for authenticating and controllablytransmitting caller ID information. The term "caller ID" is used hereinto refer generally to provision to a called party during the ringingsignal phase of call processing, of information associated with thecalling party. Unauthenticated information may be blocked or transmittedwith notice that the information has not been authenticated. For aninterLATA call, the switching facility associated with the called party,upon receiving indication via the common channel signaling network thatthe call originated at a PBX station and determining that the calledparty is a caller ID subscriber, can invoke an AIN trigger forauthentication and control in the same manner.

Additional advantages of the present invention will become readilyapparent to those skilled in this art from the following detaileddescription, wherein only the preferred embodiment of the invention isshown and described, simply by way of illustration of the best modecontemplated of carrying out the invention. As will be realized, theinvention is capable of other and different embodiments, and its severaldetails are capable of modifications in various obvious respects, allwithout departing from the invention. Accordingly, the drawings anddescription are to be regarded as illustrative in nature, and not asrestrictive.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified block diagram of a telecommunications networkhaving a common channel signaling Advanced Intelligent Network (AIN)linked with a Line Identification Data Base (LIDB).

FIG. 2 is a more detailed diagram of one of the SSP type central officesused in the preferred AIN implementation of the present invention.

FIG. 3 is a simplified block diagram of a multi-LATA PSTN network towhich PBX systems are coupled for processing of calls in accordance withthe present invention.

FIGS. 4A and 4B together comprise a simplified flow diagram for onepreferred operational embodiment in accordance with the presentinvention.

FIG. 4C is a partial flow diagram that illustrates a variation of theembodiment of FIGS. 4A and 4B.

FIG. 4D is a partial flow diagram of an additional embodiment of thepresent invention, similar in several respects to those of FIGS. 4A-4C.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is an AIN architectural environment having functional blocksrepresenting those details of the AIN network that are well known.Service Switching Points (SSPs) 11, 13, 15, 17 represent central office(CO) switching systems that are appropriately equipped programmableswitches present in the telephone network. Subscriber lines individuallyconnect SSPs to subscriber premises at which locations telephones 12 orother communication devices are connected.

SSP capable central office switching systems typically contain aprogrammable digital switch with CCIS communications capabilities. Oneexample of an SSP capable CO switch is a 5ESS type switch manufacturedby AT&T. Other vendors, such as Northern Telecom and Seimens,manufacture comparable digital switches that may serve as the SSPs. Thestructure of an exemplary SSP type CO is discussed in more detail below,with regard to FIG. 2.

The SSP type COs 11 and 13 are shown connected to a first local area STP23, SSP-COs 15 and 17 being connected to a second local area STP 25. Theconnections to the STPs are for signalling purposes. Each local area STPcan connect to a large number of the SSP-COs, as indicated for ease ofillustration merely by the circles below STPs 23 and 25. The centraloffice SSPs are interconnected to each other by trunk circuits forcarrying telephone services. The overall network may contain end officeswithout SSP functionality. Such end offices will forward calls to one ofthe SSPs if such treatment is required. Also, certain switching officeswithin the network, whether SSPs or not, may function primarily astandem type offices providing connections between trunk circuits only.

The local area STPs 23 and 25, and any number of other such local areaSTPs (not shown) communicate with a state or regional STP 31. The stateor regional STP 31 in turn provides communications with the ISCP 40. TheSTP hierarchy can be expanded or contracted to as many levels as neededto serve any size area covered by the Advanced Intelligent Network (AIN)and to service any number of stations and central office switches. Also,certain switching offices within the network, whether SSPs or not, mayfunction primarily as tandem type offices providing connections betweentrunk circuits only. Line identification data base (LIDB) 45 is atelephone data base system that stores subscriber information files forworking telephone numbers. The LIDB data base is shown linked by datalines to ISCP 40 and STP 31. Although not shown, the LIDB data base maybe directly accessed also by other STPs.

The advanced intelligent network contains a central data base 43, atISCP 40, to which reference is made for controlling switching operationsthrough multiple end offices. The central data base includes a pluralityof Call Processing Records (CPRs), each associated with a subscriber.Local and/or toll offices of the public telephone network detect one ofa number of call processing events, or triggers, both on incoming andoutgoing calls to provide a wide variety of customized telephoneservices. When an AIN capable office Service Switching Point (SSP)detects a trigger, that office suspends call processing, compiles a calldata message, and forwards that message via a common channel interofficesignalling (CCIS) link, typically SS7, to the central data base.Reference is made therein to the appropriate CPR to obtain informationnecessary for completion of the call. Thus the SSPs recognize AIN typecalls, launch queries to the ISCP and receive commands and data from theISCP to further process the AIN calls. In the illustrated embodiment,the CO-SSPs are end offices.

The links between the central office switching systems and the localarea STPs 23 and 25 are typically SS7 type CCIS interoffice datacommunication channels. The local area STPs are in turn connected toeach other and to the regional STP 31 via a packet switched network. Theregional STP 31 also communicates with the ISCP 40 via a packet switchednetwork. As illustrated in the drawing, common channel signaling uses anout of band signaling path, indicated by dotted lines, that is separatefrom the path used for voice transmission, indicated by solid lines.This signalling technology provides for faster call set-up times and amore efficient use of the voice network than prior manual signaling,dial pulse signaling or multi-frequency signaling schemes wherein thetrunk connecting the calling and the called subscribers required bothsignaling and voice transmission over the same circuitry. When a call isplaced, the voice communication is suspended while signaling istransmitted through the common channel signaling network to checkwhether the line at the destination switch is busy and to determine thevoice connection path.

The messages transmitted between the SSPs and the ISCP are formatted inaccord with the Transaction Capabilities Applications Protocol (TCAP).The TCAP protocol provides standardized formats for various query andresponse messages. Each query and response includes data fields for avariety of different pieces of information relating to the current call.For example, an initial TCAP query from the SSP includes, among otherdata, a "Service Key" which is the calling party's address. TCAP alsospecifies a standard message response format including routinginformation, such as primary carrier ID, alternate carrier ID and secondalternate carrier ID and a routing number and a destination number. TheTCAP specifies a number of additional message formats, for example aformat for a subsequent query from the SSP, and formats for "INVOKE"messages for instructing the SSP to play an announcement or to play anannouncement and collect digits and a "SEND TO RESOURCES" message toinstruct the SSP to route to another network node. Reference is made tothe copending application, Ser. No. 08/248,980, filed May 25, 1994, fora more detailed description of the AIN network.

FIG. 2 is a simplified block diagram of an electronic program controlledswitch which may be used as any one of the SSP type COs in the system ofFIG. 1. As illustrated, the CO switch includes a number of differenttypes of modules. In particular, the illustrated switch includesinterface modules 51 (only two of which are shown), a communicationsmodule 53 and an administrative module 55.

The interface modules 51 each include a number of interface units 0 ton. The interface units terminate lines from subscribers' stations,trunks, T1 carrier facilities, etc., that are physically wired to a maindistribution frame (not shown) in the central office. Where theinterfaced circuit is analog, for example a subscriber loop, theinterface unit will provide analog to digital conversion and digital toanalog conversion. Alternatively, the lines or trunks may use digitalprotocols such as T1 or ISDN. Each interface module 51 also includes adigital service unit (not shown) which is used to generate call progresstones.

Each interface module 51 includes, in addition to the noted interfaceunits, a duplex microprocessor based module controller and a duplex timeslot interchange, referred to as TSI in the drawing. Digital wordsrepresentative of voice information are transferred in two directionsbetween interface units via the time slot interchange (intramodule callconnections) or transmitted in two directions through the networkcontrol and timing links to the time multiplexed switch 57 and thence toanother interface module (intermodule call connection).

The communication module 53 includes the time multiplexed switch 57 anda message switch 59. The time multiplexed switch 57 provides timedivision transfer of digital voice data packets between voice channelsof the interface modules 51 and transfers data messages between theinterface modules. The message switch 59 interfaces the administrativemodule 55 to the time multiplexed switch 57, so as to provide a routethrough the time multiplexed switch permitting two-way transfer ofcontrol related messages between the interface modules 51 and theadministrative module 55. In addition, the message switch 59 terminatesspecial data links, for example, a link for receiving a synchronizationcarrier used to maintain digital synchronism.

The administrative module 55 includes an administrative module processor61, which is a computer equipped with disc storage 63, for overallcontrol of CO operations. The administrative module processor 61communicates with the interface modules 51 through the communicationmodule 53. The administrative module 55 also includes one or moreinput/output (I/O) processors 65 providing interfaces to terminaldevices for technicians such as shown at 66 in the drawing and datalinks to operations systems for traffic, billing, maintenance data, etc.A CCIS terminal 73 and an associated data unit 71 provide a signallinglink between the administrative module processor 61 and an SS7 networkconnection to an STP or the like, as shown in FIG. 1, for facilitatingcall processing signal communications with other COs and with the ISCP40.

The administrative module 55 also includes a call store 67 and a programstore 69. Although shown as separate elements for convenience, these aretypically implemented as memory elements within the computer serving asthe administrative module processor 61. For each call in progress, thecall store 67 stores translation information retrieved from disc storage63 together with routing information and any temporary informationneeded for processing the call. For example, for a switch based Centrextype service, the call store 67 would receive and store extension numbertranslation information for the business customer corresponding to anoff-hook line initiating a call. Translation tables, includingsubscribed class features are loaded into the store with each call. Theprogram store 69 stores program instructions which direct operations ofthe computer serving as the administrative module processor.

FIG. 3 is a block diagram of a multi-LATA PSTN network to which PBXsystems are coupled for processing of calls in accordance with thepresent invention. It should be recognized that the figure isconsiderably simplified for explanation purposes and that the fullnetwork and operating environment for the invention may comprisemultiple central offices, diverse interconnections, and provisions forreliability through redundancy, all of which need not be shown fordeveloping an understanding of the invention. Elements of this figurethat are in common with those of FIG. 1 are referenced by the samenumbers. Telephone station 16 is equipped with caller ID display unit18, which may embody any commercially available alphanumeric displayunit, and connected by a subscriber line to central office SSP 15. Forpurposes of explanation of the invention, station 16 is assumed to be asubscriber of caller ID, a status which is programmed into thesubscriber profile at SSP 15. Calls routed to station 16 may originatewithin its LATA 40 or from a remote LATA 42.

As illustrated, LATA 40 includes SSPs 11, 13 and 15 that are linked byvoice trunks. Also included is tandem switching facility 48 that is thepoint of presence for interexchange carrier network 46. The LATA isserved by the common channel signaling SS#7 AIN network that includes,for purposes of illustration, STPs 25 and 31, ISCP 40, and LIDB 45. SSP11 is shown connected by a subscriber line to telephone station 12 andby PBX trunk 9 to PBX 8. PBX 8 is an on premises system that serves aplurality of telephone stations 10 over a private voice network.

Remote LATA includes SSP 17 coupled by voice trunk to tandem 47, whichis the point of presence for interexchange network 46. STP 24 is part ofa common channel signaling network that may be coupled in any of variousways, for example by direct connection or through an intermediarynetwork, to the AIN network of LATA 40. FSSP 17, while in actualityservicing a large number of subscribers, is shown connected by PBX trunk9' to PBX 8'. PBX 8' is a private voice network system that serves aplurality of telephone stations, one of which is shown at 10'.

Operation of the invention is described with reference to the flowcharts of FIGS. 4A-4D. FIGS. 4A and 4B together comprise one preferredoperational embodiment. A call is initiated to called party subscriberstation 16 by telephone station 10 or telephone station 10' atrespective PBX systems 8 or 8'. The call may thus originate from alocation within the same LATA 40 as that of the called party or from astation at a remote LATA 42. The call will be output by the PBX systemover trunk 9 or 9' to the associated switching facility 11 or 17. ThePBX system may be programmed to output, in addition to the dialedsignals of the calling party, caller ID information data over a datachannel via the PBX trunk. The textual content and originating number ofthe caller ID information can be made specific to the particular callingstation at the discretion of the user or as determined by PBX systempersonnel. Caller ID information may be limited to text if the userchooses not to disclose the originating number. In that instance, nocaller ID telephone number is transmitted. Conversely, the user mayprefer to merely identify the internal number of the dialing station orthe main PBX dial-in number. Each outgoing call thus can includespecialized caller ID information or, in the absence thereof, the numberassociated with the PBX terminal along with the dialed signals.

At step 101, caller ID information and dialed signals are received fromthe PBX 8, 8' by the associated switching facility 11, 17. The switchcompares the caller ID telephone number, if any, received with thenumber assigned to the PBX terminal by the PSTN, at step 103. If thenumbers are the same, or if no caller ID number is received, routing ofthe call takes place in the normal fashion with the received caller IDinformation transmitted to the called party station, at step 105. If theswitch detects a caller ID number that does not match the assigned PBXterminal number in step 103, call processing is temporarily suspendedand triggering of the AIN network occurs at step 107, wherein a TCAPmessage is sent from the switch to the ISCP via the common channelsignaling network. The ISCP data base is accessed for the callprocessing record of the PBX subscriber.

The PBX call processing record includes a list of internal telephonenumbers for the PBX stations, as well as alternate numbers that havebeen approved for use as caller ID displayed numbers. Such approval canbe based upon various criteria such as, for example, agreement by thesubscriber of the alternate number. At step 109, a comparison is madebetween the received caller ID number, if any, and the numbers listed inthe PBX CPR at the ISCP. If a match results, the call is routed to thedialed destination with the caller ID information transmitted therewith.

A failure of a match determination in step 109 is indicative that eitheran unauthenticated number or no number has been included in the callerID information. Various possibilities include (i) that only textualidentification was intended to be received, (2) that an error was madein programming an incorrect number in the PBX system, and (3) fraudulentor intentional insertion of a non-approved working number has beengenerated by the PBX system. If no match is determined in step 109, theLIDB data base is accessed at step 111. At step 113, determination ismade of whether the received caller ID information contains a numberthat matches a working telephone number in the LIDB data base. Uponfailure of such a match, processing of the call will continue withtransmission of the received caller ID information to the called party.As the called party will have displayed either text alone or anon-working number, a call to the displayed number by the called partycan not be completed unintentionally to a third party. The called partymay recognize from the displayed information that a mistake exists andbe able to discern an accurate number for identification purposes or fora return call.

A matching condition in step 113 indicates that the received caller IDinformation includes a working number that has not been authorized.Transmission of such information alone would not be desirable as theinformation, whether fraudulent or simply inaccurate, could lead thecalled party to initiate a call that would be a nuisance to bothparties. Thus, at step 115, the call is routed to its dialed destinationwith transmission of the caller ID information blocked. The called partycan thus decide whether to answer an unidentified call and not be facedwith returning a call that may become a nuisance.

FIG. 4C is a partial flow diagram that illustrates a variation of theembodiment of FIGS. 4A and 4B. Operation differs only with respect that,in response to a matching working number determination in step 113,transmission of the caller ID information, together with a message thatthe information has not been authorized, occurs at step 117. The calledparty is thus made aware that the received number is not accurate andhas the opportunity to recognize a mistake, such as transposed digits.Received textual information may further clarify a mistake in thegeneration of the caller ID information.

FIG. 4D is a partial flow diagram of an additional embodiment, similarin several respects to those of FIGS. 4A-4C. Rather than provide PBXcall processing records in the ISCP, authorized caller ID numbers areassociated with the PBX in the LIDB data base. Operation proceeds in thesame manner as steps 101 through 105 of the flow diagram of FIG. 4A.However, in this embodiment, if the switch detects a caller ID numberthat does not match the assigned PBX terminal number in step 103, callprocessing is temporarily suspended and triggering of the AIN networkoccurs at step 119, to access the LIDB data base via the common channelsignaling network. If a received caller ID number is not an authorizednumber in the LIDB data base, as determined by matching the receivednumber against the listed numbers in step 121, the call is routed to itsdialed destination with transmission of the caller ID informationblocked, at step 123. Alternatively, transmission of the caller IDinformation, together with a message that the information has not beenauthenticated, can be made to the called party, as provided at step 117in FIG. 4C.

In this disclosure there is shown and described only the preferredembodiments of the invention and but a few examples of its versatility.It is to be understood that the invention is capable of use in variousother combinations and environments and is capable of changes ormodifications within the scope of the inventive concept as expressedherein. For example, for inter LATA calls originating from carriers thatdo not normally provide PBX authentication, triggering of the ISCP database or LIDB data base can be initiated by the central office switchingfacility that is associated with the called party. The switchingfacility determines from its record profile for the called partysubscriber that caller ID service has been subscribed for an incomingcall. During processing of the call, the called party switching facilitycan determine from signalling received from the calling switchingfacility whether caller ID information generated by the originating PBXcontains a telephone number that matches the assigned main PBX number.If a set bit in the received signalling is indicative that no such matchexists, the called party switching facility can initiate authenticationin the manner described above with respect to the embodiments of FIGS.4A-4D.

What is claimed is:
 1. A method for supplying calling party informationfor a telephone call originating from a PBX system, coupled to a publicswitched telephone network (PSTN) and having a telephone number assignedto its terminal address, to a called party station at a remote location,comprising the steps of:receiving from said PBX, at a location in saidPSTN, dialed called party telephone number input and calling partyidentifying information generated by said PBX; determining whether saidcalling party identifying information contains a telephone number thatmatches the PBX assigned telephone number; in response to a non-matchingcondition in said determining step, accessing a data base; comparingsaid calling party identifying information with said data base; routingthe call to said called party station; and in response to a matchbetween a number contained in said calling party identifying informationand a number found in said data base in said comparing step,transmitting said calling party identifying information to said calledparty station.
 2. A method as recited in claim 1, wherein said PSTNcomprises an advanced intelligent network having at least one integratedservices control point (ISCP), and wherein said accessing stepcomprises:triggering a PSTN switching facility at said location that isassociated with said PBX system; and sending a query message from saidswitching facility to said data base, said data base being remote fromsaid switching facility.
 3. A method as recited in claim 2, furthercomprising the step of transmitting said calling party identifyinginformation, without accessing said data base, in response to a matchingcondition in said determining step.
 4. A method as recited in claim 2,further comprising the step of blocking transmission of said callingparty identifying information to said called party station, in responseto a failure to match a number contained in said received informationwith a number in said data base in said comparing step.
 5. A method asrecited in claim 4, wherein said blocking step comprises sending aresponse message from said ISCP to said switching facility.
 6. A methodas recited in claim 2, further comprising the steps of:transmitting saidcalling party identifying information to said called party station; andin response to a failure to match a number contained in said callingparty identifying information to a number found in said data base insaid comparing step, transmitting to said called party station a messageindicating that said information is not authenticated; whereby thecalling party identifying information generated by said PBX and theunauthenticated status thereof can be displayed at the called station.7. A method as recited in claim 2, wherein said ISCP includes said database and, in response to a failure to match a number contained in saidreceived information with a number in said data base in said comparingstep, further comprising the steps of:accessing a line identificationdata base (LIDB) in said PSTN that is remote from said ISCP; determiningfrom the LIDB whether the number contained in said received informationis a working telephone number; and transmitting said calling partyidentifying information to said called party station in response to anon-working number determination in said determining step.
 8. A methodas recited in claim 7, further comprising the step of blockingtransmission of said calling party identifying information to saidcalled party station, in response to a working number determination insaid determining step.
 9. A method as recited in claim 7, furthercomprising the steps of:transmitting said calling party identifyinginformation to said called party station; and in response to a workingnumber determination in said determining step, transmitting to saidcalled party station a message indicating that said information is notauthenticated; whereby the calling party identifying informationgenerated by said PBX and the unauthenticated status thereof can bedisplayed at the called station.
 10. A method as recited in claim 2,wherein said data base is a line identification data base (LIDB) in saidPSTN that is remote from said ISCP, and wherein said accessing stepfurther comprises initiating a lookup in said LIDB by said ISCP.
 11. Amethod as recited in claim 1, wherein said PSTN comprises an advancedintelligent network having at least one integrated services controlpoint (ISCP) interconnecting a plurality of PSTN switching facilitiesvia a common channel signaling link, and wherein said accessing stepcomprises:triggering a PSTN switching facility that is associated withsaid called party station; and sending a query message from saidswitching facility to said data base via said common channel signalinglink.
 12. A method as recited in claim 11, wherein said PBX system iscoupled to switching facility in a local access transport area (LATA)that is different from the called party associated switching facilityLATA.
 13. In a public switched telephone network having a plurality oftelephone switching facilities, subscriber telephone lines forconnecting said facilities to respective associated subscriber stations,and at least one PBX trunk for connecting one of said switchingfacilities to an associated subscriber PBX system that serves aplurality of stations connected thereto, the improvementcomprising:receiving means for receiving called party telephone numberinput and calling party identifying information generated by said PBXsystem for a call placed from a calling station connected to said PBXsystem; determining means for determining whether said received callingparty identifying information is a previously authorized representationfor identifying the calling station; and routing means for routing saidcall to its dialed called party destination with said calling partyidentifying information in response to a determination by saiddetermining means that said calling party identifying information is anauthorized representation of the calling station.
 14. A network asrecited in claim 13, wherein said routing means comprises blocking meansfor blocking transmission of said calling party identifying informationin the routed call to the called party in response to a determination bysaid determining means that said calling party identifying informationis not an authorized representation of the calling station.
 15. Anetwork as recited in claim 13, wherein said routing means comprisesmessaging means for generating message information indicating that saidcalling party identifying information is not an authorizedrepresentation of the calling station in response to a determination ofnonauthorization by said determining means, said routing means includingsaid calling party identifying information and said message informationin the routed call;whereby the calling party identifying informationgenerated by said PBX and the nonauthorized status thereof can bedisplayed at the called party subscriber station.